Fig. 7: Osr1-deficient FAPs acquire a pro-fibroblastic identity and regulate myogenesis via the ECM.

a, b Heat maps depicting extracellular matrix (ECM) related genes at 3 dpi and 7 dpi in control or Osr1cKO FAPs (n = 2). c Venn diagram showing overlapping gene deregulation between mdx FAPs and Osr1cKO FAPs at 3 dpi or 7 dpi. d Immunolabeling for collagen VI and fibronectin (Fn1) on in vitro recombined FAPs after 6 days of culture. Quantification of the stained areas shown right (n = 4). e Immunolabeling for Perilipin A/B on in vitro recombined FAPs after 6 days of culture. Quantification of Perilipin+ cells shown right (n = 4). f Schematic depiction of the in vitro matrix deposition assay. g Immunolabeling for Collagen VI and staining for f-actin using phalloidin on C2C12 cells cultured for two days in differentiation medium on dECM from control or Osr1 cells from contralateral hindlimbs of injured 7 dpi animals. Quantification of f-actin+ cell size shown right (n = 3). h Immunolabeling for Collagen VI and MHC on C2C12 cells cultured for 5 days in differentiation medium on dECM from control or Osr1 in vitro recombined cells. Quantification of fusion index shown right (n = 4). i Schematic overview of Osr1cKO effects. Data are presented as mean ± SEM; P‐value calculated by two‐sided unpaired t test; *p < 0.05, **p < 0.01, ****p < 0.0001. N‐numbers indicate biological replicates (mice per genotype). Scale bars: 100 μm in (d, e); 50 μm in (g, h).